Marcus Harris is the only member of Australia's top six who can be certain what position he'll walk out to bat in Thursday's day-night Test against Sri Lanka, with the make up of the side still completely up in the air. Harris will open at the Gabba, but is seemingly the only batsman locked into a set spot after Marnus Labuschagne admitted he still didn't know if he'd be selected. The hosts still have two extra batsmen in their 14-man squad, an unrivalled situation for any home Test in recent memory with five batsmen fighting to fill three holes. Usman Khawaja will definitely be picked after opening in the fourth Test against India in Sydney, although he said on SEN Radio on Tuesday he expected to move back to No.3 with Joe Burns and Matt Renshaw hoping to partner Harris. Travis Head is also seemingly assured of a spot after being named as vice-captain alongside Pat Cummins, but it's unknown exactly where in the middle order he'll bat. Peter Handscomb, Aaron Finch and Shaun and Mitch Marsh have all been axed from the batting line up that failed to score a century against India. That leaves Burns, Renshaw, Labuschagne and rookies Kurtis Patterson and Will Pucovski fighting it out for the final three spots, with anyone's guess as to what numbers they will fill if picked. "There's no team been selected yet so anywhere in the order if I am selected I would be happy to bat," Labuschagne said before an evening training session at the Gabba on Tuesday. "I wouldn't say it's a strange feeling. It's a good thing to have competitiveness around the squad. "We are all happy for each other and want each other to play, but at the end of the day there's only 11 who get to walk onto the field." Labuschagne at least looks the most likely of the quintet, after having been parachuted into No.3 at the SCG against India and looking sound before being dismissed for 38. He's also feeling the advantage of a better preparation than he did for Sydney, when he was called into the squad just days before the match started. The 24-year-old hit a half-century in the second innings of a tour match against Sri Lanka in Hobart last week and is returning to his home venue at the Gabba. "In the preparation I think it helps because you are working together with everyone and preparing with the contentiously," he said. "When I came in (for Sydney) I came in from just watching the Test on TV and gaining the information that way whereas being in the squad." Meanwhile Jhye Richardson is favoured to make his Test debut as Australia's third quick ahead of Peter Siddle, with Josh Hazlewood ruled out of the two-Test series due to a back injury. Australian Associated Press

Uncertainty surrounds makeup of Test side

Marnus Labuschagne is unsure if he will play against Sri Lanka at the Gabba.

Marcus Harris is the only member of Australia's top six who can be certain what position he'll walk out to bat in Thursday's day-night Test against Sri Lanka, with the make up of the side still completely up in the air.

Harris will open at the Gabba, but is seemingly the only batsman locked into a set spot after Marnus Labuschagne admitted he still didn't know if he'd be selected.

The hosts still have two extra batsmen in their 14-man squad, an unrivalled situation for any home Test in recent memory with five batsmen fighting to fill three holes.

Usman Khawaja will definitely be picked after opening in the fourth Test against India in Sydney, although he said on SEN Radio on Tuesday he expected to move back to No.3 with Joe Burns and Matt Renshaw hoping to partner Harris.

Travis Head is also seemingly assured of a spot after being named as vice-captain alongside Pat Cummins, but it's unknown exactly where in the middle order he'll bat.

Peter Handscomb, Aaron Finch and Shaun and Mitch Marsh have all been axed from the batting line up that failed to score a century against India.

That leaves Burns, Renshaw, Labuschagne and rookies Kurtis Patterson and Will Pucovski fighting it out for the final three spots, with anyone's guess as to what numbers they will fill if picked.

"There's no team been selected yet so anywhere in the order if I am selected I would be happy to bat," Labuschagne said before an evening training session at the Gabba on Tuesday.

"I wouldn't say it's a strange feeling. It's a good thing to have competitiveness around the squad.

"We are all happy for each other and want each other to play, but at the end of the day there's only 11 who get to walk onto the field."

Labuschagne at least looks the most likely of the quintet, after having been parachuted into No.3 at the SCG against India and looking sound before being dismissed for 38.

He's also feeling the advantage of a better preparation than he did for Sydney, when he was called into the squad just days before the match started.

The 24-year-old hit a half-century in the second innings of a tour match against Sri Lanka in Hobart last week and is returning to his home venue at the Gabba.

"In the preparation I think it helps because you are working together with everyone and preparing with the contentiously," he said.

"When I came in (for Sydney) I came in from just watching the Test on TV and gaining the information that way whereas being in the squad."

Meanwhile Jhye Richardson is favoured to make his Test debut as Australia's third quick ahead of Peter Siddle, with Josh Hazlewood ruled out of the two-Test series due to a back injury.